1. Field of the Invention
This invention relates to a carbon monoxide-oxygen fuel cell. More particularly it relates to the solution for the cathode of the fuel cell and the cell constitution thereof.
2. Description of the Prior Art
If a CO/O.sub.2 fuel cell (carbon monoxide and oxygen being denoted as CO and O.sub.2, respectively) is constituted using CO as its fuel and O.sub.2 as its oxidizing agent, the cell reaction at the fuel pole or anode and the oxygen pole or cathode is expressed by the following reaction equations (1) and (2): EQU Anode (fuel pole) CO+H.sub.2 O.fwdarw.CO.sub.2 +2H.sup.+ +2e .sup.-( 1) EQU Cathode (oxygen pole) 1/2O.sub.2 +2H.sup.+ +2e.sup.- .fwdarw.H.sub.2 O (2)
If this CO/O.sub.2 system fuel cell comes into existence, this is characterized in that (i) the theoretical electromotive force per a single cell is higher and (ii) the ideal heat efficiency .epsilon..sub.T is higher than those in the case of hydrogen-oxygen fuel cell (.epsilon..sub.T =0.829 in the case of H.sub.2 /O.sub.2 fuel cell, whereas .epsilon..sub.t =0.909 in the case of CO/O.sub.2 fuel cell, each at 25.degree. C.).
However, the non-complexed or uncoordinated CO molecule is an electrochemically inert substance; hence the substance cannot advance, as it is, the anodic oxidation reaction of CO as shown in the equation (1) toward the right side. Thus, it has been impossible to constitute a CO/O.sub.2 fuel cell.
If it is intended to use such an electrochemically inert CO as a fuel for the fuel cell, CO can be reacted with H.sub.2 O by means of a shift converter to convert the CO and H.sub.2 O into H.sub.2 gas and thereby constitute a H.sub.2 /O.sub.2 fuel cell. An example of the constitution of a conventional CO/O.sub.2 system fuel cell according to this process, and its flow are shown in FIG. 7. In this figure, a CO-containing gas 8 as a fuel is first sent to a high temperature shift converter 2 where CO is reacted with steam 17 at 350.degree. C. to 370.degree. C. to convert most of CO and H.sub.2 O into H.sub.2, and further sent to a low temperature shift converter 3 where the resulting gas is reacted at 200.degree. C. to 230.degree. C. to reduce the concentration of CO down to an allowable one, followed by feeding the resulting gas to an anode 5 as a H.sub.2 -rich gas and after a definite reaction, discharging the resulting gas as an exhaust one 10. On the other hand, air 11 is fed to a cathode 6, and after a definite reaction, discharged as an exhaust gas 12. In this figure, numeral 1 shows a cell body, 4 shows an electrolytic chamber, 7 shows a load and 16 shows the transfer direction of hydrogen ion. As described above, the conventional process has had uneconomical drawbacks in that it is necessary to provide a two stage high temperature and low temperature shift converters 2 and 3 and also a large quantity of water is required for the CO/H.sub.2 conversion.